Motion-converting mechanism



Feb. 28, 1939. c. K. GRAVLEY MOTION-CONVERTING MECHANISM Original Filed April 12, 193'? 3 sheQw-sheet 1 ATTORNEY Feb. 28, 1939. c, K GRAVLEY Y 2,149,216

MOTION-CONVERTING MECHANISM Original Filed April 12, 1937 3 Sheets-Sheet 2 Array/v1.

Feb. 28, 1939. c, K GRAVLEY 2,149,216

MOT ION CONVERTING MECHANI SM Original Filed April 12, 193'? 3 Sheets-Sheet 3 25 H6. A). n 25 25 Arranwrr Patented Feb. 28, 1939 PATENT OFFICE MOTION-CONVERTING MECHANISM Charles K. Gravley, Cleveland, Ohio, assignor to The Brush Development Company, Cleveland. Ohio, a corporation of Ohio Application April 12, 1931, Serial No. 130,339 Renewed July 26, 1938 QCiaims.

This invention relates to new and improved means for magnifying and for reducing linear motion and for converting, linear motion into angular motion, and vice versa, and particularly to such motion-converting means adapted to teiifect a great magnification or reduction of mo- My improved mechanism has been developed in connection with piezo-electric apparatus for coupling piezo-electric energy converters to driven or driving devices having angular motion, which in some applications may be relatively large, and for purposes of explanation and illustration I shall describe my invention as embodied in a novel form of directly-recording piezo-electric oscillograph.

Piezo-electric energy converters are in general characterized by small displacements and relatively great mechanical forces developed under the application of electromotive forces to the converter and conversely by the great mechanical forces required to generate electromotive forces and the small distances through which the mechanical forces act. In many possible appli- 25 cations of such energy converters it is desirable to obtain or apply smaller mechanical forces and greater motions. Simple lever systems have been found satisfactory for moderate ratios of transformation but high ratio levers in general introduce excessive loss due to their flexibility, and to play and friction in bearings, and the inertia of such levers often prohibits their use at all but very low frequencies. Other lever arrangements have been devised which have no relatively moving bearing parts and depend on the bending of some elements in lieu of pivot action, but they may introduce undesirable spring effects.

An object of this invention is to provide a mechanism for magnifying or reducing linear 40 motion having no sliding or knife edge bearings and characterized by a minimum of 10st motion.

Another object of the invention is to provide an aperiodic mechanism for magnifying or reducing linear motion.

A further object of the invention is to provide a mechanism adapted to effect large magnification or reduction of linear motion and characterized by (a) minimum inertia effectsand (17) great compactness.

Another object of the invention is to provide a mechanism adapted to convert linear motion into angular motion, and vice versa, and having one or more of the following characteristics, to-wit, (a) operation with a minimum of lost motion. 55 (b) aperiodic operation, (c) minimum inertia effects in operation, and (d) great structural compactness.

With the foregoing and other more or less ancillary or incidental objects in view my invention consists in certain forms and combinations of parts which are set forth in the following de-' tailed description in connection with the accompanying drawings.

Fig. 1 is aperspective view of a piezo-electrically actuated directly recording oscillograph 1o embodying my invention with the record paper and rolls indicated diagrammatically.

Fig. 2 is a plan view of the mechanism shown in Fig. 1 with the record paper and rolls omitted.

Fig. 3 is a front elevation of the-mechanism 15 shown in Fig. 2.

Fig. 4 is a vertical section of the same mechanism on line H of Fig. 2.

Fig. 5 is an enlarged fragmentary front elevation of the motion converting mechanism.

Fig. 6 is an enlarged fragmentary section on the line 4-4 of Fig. 2.

Fig. '7 is an enlarged section on the line of Fi 6.

Fig. 8 is an enlarged section on the'line 8-8 25 of Fig. 6.

Fig. 9 is a front elevation, in unbent form, of one of three similar flexible members of the motion-converting mechanism.

- Fig. 10 is an edge view. of the same.

Fig. 11 is an enlarged perspective view of the spindle member of the motion-converting mechanism with one ofthe flexible members in operative position thereon, the parts being viewed from one side.

Fig. 12 is an enlarged perspective view of the same parts shown in Fig. 11 but viewed from the opposite side.

Fig. 13 is an enlarged perspective view similar to that of Fig. 11 but showing a modified form of construction.

Fig. 14 is an enlarged plan view of the spindle and pen arm parts of the device shown in Fig. 13.

Fig. 15 is a plan view corresponding to Fig. 2 but illustrating an application of my invention to a piezo-electrically actuated relay.

The general character of the apparatus shown in Figs. 1 to 10 may be seen from an inspection of Fig. l. The numeral I designates as an entirety a box-like casing and supporting structure within which is hermetically enclosed and operatively mounted a piezo-electric unit of the flexing type designated by the numeral 2. The free portion of the piezo-electric unit is connected by a pin (not visible in Fig. 1) which is mounted for timed driving mechanism (not shown).

endwise movement through a wall of thecasing and is operatively connected to a mechanism designated as an entirety by 3 which is mounted on the wall of the casing l and is adapted to convert the endwise or linear movement of the'drive pin to angular movement to effect desired swinging movement of an oscillograph arm 6 connected to the mechanism 3. The arm 5 is in'the form of a capillary tube fitted at its free end with a suitable capillary pen point (in formed of glass. The pen point is arranged to contact a strip of paper 5 which is moved over rolls 6, 6 by suitably An ink well 1 is mounted on the casing l and a flexible capillary rubber tube 8 connects the ink well with the inner end of the capillary arm 4 to supply the pen point with ink. When 'an alternating or fluctuating electromotive force is applied to the piezo-electric unit the pen point traces a graph of such alternations or fluctuations on the paper strip 5 as it moves over the rollers 6, 6.

Referring now in further detail to the construction of the apparatus, the casing l comprises a main body part la. and a cover plate lb which is attached by screws 9, 9 to the part la with two interposed gaskets l0, ll) of rubber or the like adapted to form a hermetic joint between the casing members.

The piezo-electric unit 2 may be of various suitable forms of construction, such, for example, as that disclosed in United States Patent 1,803,275. This plate-like unit is square in form and is mounted on the enclosing casing at three comers between the unit 2 and the body part la of the casing. A metal plate l2 formed with a semispherical or rounded boss is attached to the other relation to the casing, thus obviating lost motion in the mounting of the unit 2. The crystal plates or elements of the unit 2 are so oriented that the axes of expansion and contraction coincide with the diagonals of the unit on which the three points of support are arranged. This principle of mounting is fully disclosed and explained in United States Letters Patent of A. L. Williams, No. 2,105,011, granted January 11, 1938.

To the fourth or free corner of the crystal unit is secured a drive pin I which extends through an opening l5 in the cover plate lb, this opening being sealed by a plug of soft rubber IS. The rubber plug surrounds and seals the drive pin I but is adapted to deform sufficiently to permit the necessary endwise movement of the pin. Electric leads l1, I] of the crystal unit are brought out between gaskets l9, II! to terminals l9, l8 which are secured to an insulating plate l9 mounted on the cover plate lb.

. The operation of such piezo-electric units is described in the above mentioned patent and application and it will be sufficient for the purpose of this application to state that a potential dif arsenic ference applied between terminals l8, l8 causes a displacement of the drive pin is in a direction normal to the face of cover plate lb and the direction of the motion is determined by the polarity. An alternating potential difference applied between terminals l8, l8 causes a vibratory movement of drive pin l4. Conversely, mechanical displacement of drive pin l5 results in a corresponding potential difference between terminals l8, l8. Thedisplacement of drive pin M on application of an E, M. F. to terminals l8, l8 actuates motion-converting mechanism 3.

The motion-converting mechanism 3 comprises a spindle 26, shown in enlarged perspective in Figs. 11 and 12, having convexly curved surfaces 2 1, ii of one radius and a convexly curved surface 22 of slightly different radius. The spindle is operatively supported from a block 23 carried by a plate 26 adjustably mounted on casing l. The supportof the spindle is efiectedby ribbon-like flexible members 25, 25 of thin spring steel or the like. As shown in Fig. 9, fiemble members 25 are fork shaped and comprise end elements25a and 25b, 25b and a connecting intermediate element portion 25c. The said end elements are provided with reinforcing tabs 25d and 25e which are soldered to their ends. The flexible members are secured to supporting block 23 by pins 28, 26 en'- gaging holes 25f in tabs 25c, and are looped around curved surfaces 2| of the spindle in a manner similar to that indicated in Figs. 11 and .12, so that elements 25b, 25b are in contact with one curved surface portion and element 25a is in contact with another curved surface portion of the same radius. Bow-shaped springs 21, 2'1 engage holes 28, 2B of block 23 and holes 25g, 25g of the flexible members, and are arranged to hold the flexible members in tension and firmly against the ridge 23a of block 23. Fig. 7 (sectional view through a curved surface 2| of the spindle) shows how the spindle is supported by the block, flexible member and spring. The spindle thus supported, when it turns, also rolls on a plane defined by the straight portions of theribbon-like members 25, 25, such'rolling being permittedby the simultaneous winding and unwinding of the flexible members on different curved surface portions of the same radius.

To effect such rolling motion of the spindle it is provided with a. flexible member 29 similar to members 25 and comprising end elements 29a and 29b, 29b and intermediate element 290. As shown in Figs. 11 and 12, member 29 is looped around the curved surface 22 of the spindle and has one end secured by a pin 30 to a coupling 3| which in turn is fast on the end of the drive pin H. A tension spring 32, similar to springs 21, holds the flexible member in tension with its straight end elements in a plane tangent to curved surface 22 and parallel to the plane defined by the straight end elements of the members 25.

When the piezo-electric unit is energized the drive pin I4 is given endwise movement and such .movement, transmitted to the flexible member 29 wrapped around the surface 22 of the spindle, applies to the spindle a force tangent to the surface 22. Simultaneously, the flexible members 25- caused toroll on a plane defined by the straight portions of the members 2|, as previously explained. This rolling motion is a combination of angular motion and lateral displacement of surfaces 2| and 22 and the relation is expressed by the formula:

(I) R-r of the arm 4.

As the spindle 23 mils along. the plane determined by the' tensioned members 25, 25, for a given angular motion 0 the axis of curvature of the cylindrical surfaces 2i moves laterally a distance t expressed by the formula:

The relation between the distance t and the movement a: of the drive member I4 is obtained by substiuting the value of 0 from Equation (1) in Equation (2) and is:

Thus if the pen arm were made of a length such that the pen point falls at the axis of curvature of curved surfaces 2i, the pointwould have a. straight line motion. And if R-r is made small in comparison with r then the motion of the pen point will be large for a small motion of the drive member. Thus the mechanism can be used as means for magnifying rectilinear motion.

If the end of the arm 4 is extended a distance it beyond the'axis of curvature of the cylindrical surface 2i the motion of the point at the end of the arm will be made up of two components, namely, that due to the motion t of the axis of curvature of the spindle and an arcuate motion of a length at or X R--r due to the angular movement of the arm about the said axis. The total travel m of the pen point In is then:

7 As one or the other component is made large in comparison with the other, the linear motion a of the drive pin ll may be converted to magnified forms ranging from a straight line to substantially the arc of a circle, as the exigencies of the design may require. With the spindle radii in the order of 0.50" and a difference in radii in the order of 0.01" and a pen arm about 3" long, the magnification is in the order of 300 to 1 and the path of the pen point is approximately the arc of a circle.

It will be apparent from the foregoing description that I am enabled. by disposing both the supporting members "and the driving member 23 on one side of the spindle, to secure the effect of an exceedingly short lever arm for the purpose of attaining great multiplication of motion. The difference in the radii of the curved surfaces 2l, 2i and 22 of the spindle corresponds to the length of the short arm of a simple lever and it is-obvious that this dimension can be reduced.

, to an exceedingly small value and that it is practically impossible with a simple lever mechanism to attain a lever arm comparable in shortnessto this differential dimension which is so readily attained in my improved mechanism. By means of my improved construction an enormous multiplication of motion can be secured with a swinging arm of very moderate overall length and correspondingly small weight and inertia effects.

To permit the adjustment of the'angular position of spindle 20 the adjustment-plate 24 is provided with pointed feet 33, 33 engaging recesses la, la in cover plate lb and with an adjusting screw 34. A spring 35 is provided to hold the adjustment plate in adjusted position, Rotation of screw 34 causes the whole spindle assembly to move toward or away from cover plate lb, thus correspondingly rotating spindle 20. It will be observed that the flexible members 25 and 28 are held under fixed tension by their respective springs 21 and 32. The forces applied to the mechanism by the crystal unit 2 and the reaction on the support block 23 are in such direction as to increase or decrease the tension in the flexible members. By making the tension maintained in said members by their respective springs greater than the forces applied to the flexible members by the crystal unit 2, the device is made to operate with substantially no play or backlash. The motion-amplifying mechanism 3 has no sliding bearings or joints to wear and become loose and chatter. In the direction in which forces are applied thereto in operation the mechanism is very rigid and resistant and any spring action introduced by the flexible members is negligible. If desired, positive means, such as the pin 36 set in the back of the spindle and engaging a hole in the flexible member,'may

, be provided to prevent slippage of the flexible member in relation to the spindle, but the frictional engagement between these parts is usually sufllcient for this purpose.

Where the mechanism is required to operate at high speed, as for recording relatively high frequency vibrations, it is important to keep the inertia effects of the parts as low as possible and, to this end, to reduce the weight of spindle and pen arm 4 to a minimum. For this reason the spindle is preferably made in the form of a section of a hollow cylinder or tube, the width of the sectionbeing made suiilcient to afford the necessary curved surface for the rolling motion through the necessary angle. The spindle may to advantage be made of aluminum or other light weight metal. The capillary tube forming the 4 areasre uct known in the trade as viscoloid, this bar having one end inserted into the slot 2M of the spindle 20 and its other end secured to a bracket 38. Angular vibration of spindle 26 causes a twisting of the bar 81 and the latter absorbs energy from the vibrating system. When the motion-converting mechanism is used to actuate a pen, some damping is provided by the friction of the pen I point on the paper, but this damping may be a m variable factor due to variations in paper and other causes and it may, therefore, be desirable to provide the additional damping at the spindle.

I prefer to make the curved portion 22 of the spindle of slightly larger radius than the por- 5 tions 2!. However, it is feasible to make the surface 22 of smaller radius than the portions 2| and this results in reversal of the direction of angular motion of the spindle for a given direction of motion of the driving pin it.

an While I prefer to make the flexible members '25 and 29 of thin spring steel, it will be understood that other materials such, for example, as phosphor bronze, may be used. Furthermore, it is not necessary that the flexible members he made 25 in the forms shown.

From the foregoing description'the operation of the oscillograph will readily be understood. Assuming that the source of the variable electric potential to be studied is connected to the ter- 30 'minals l8, it of the device and-that the record sheet 5 has been arranged in operative position on the supporting and driving rollers and that the well i has been supplied with ink, the variable voltage applied to the electrodes of the crystal 35 unit causes the latter to vibrate with resultant motion of the drive pin H which causes the previously described rolling motion of the spindle 20 and the corresponding vibratory swinging of the pen arm I so that a continuous graph is traced 40 upon the sheet of paper as the latter is moved under the pen point. Although the amplitude of the vibratory motion of the crystal unit is relatively small, the amplification of this motion by the mechanism 3 is so great and is so accurate by 45 reason of the absence of substantially all lost motion in the mechanism, that a graph is traced by the pen upon a relatively large scale. This graph will faithfully represent the variable voltage impressed upon the piezo-electric unit if use is made 50 of a record sheet suitably ruled to compensate for the arcuate form of motion of the pen point. Furthermore, the weight and inertia effects of the moving parts of-the mechanism are sumciently lowto permit operation at suillciently high fre- Il quencies to give the instrument a relatively large range ofusefulness. One use to which the apparatus has been put is thestudy of mechanical vibrations of various kinds which are picked up by suitabledevlces adapted to convert the vibra- 60' tory motion into vibratory electricv currents or potentials which in after suitable amplification, are impressed upon the crystal unit 2 ofthe apparatus. The apparatus produces a graph'c record of the vibrations studied and the advan- 65. tage of an apparatus capable of thus directly recording such phenomena is obvious. Another .typical use of the apparatus is as adirectly recording electrocardiograph, the apparatus being capable of making-direct records of the suitably 7o amplified electric currents generated by the heart or by the human body in unison with heart beats. Variousother uses of the apparatus will be apparent from the characteristics of the apparatus which have been set forth. 1 In the foregoing discussion and in connection with the development of mathematical equations applicable to the operation of the motion-converting mechanism, it has been pointed out that in case the pen point actuated by the spindle is disposed on the axis of the spindle the graph 5 traced by the pen point becomes a straight line. To illustrate this special case as well as certain modified details of construction I have shown in Figs. 13 and 14 a portion of a modified form of mechanism. In this construction the spindle 39 has curved surfaces 50, $9 with the same radius of curvature and a curved surface 5 iof somewhat larger radius. 62 represents a drive pin to which is rigidly attached a clip 83 and flexible elements 44, M, with their ends reenforced as in the case of 15 the flexible members 25 and 29 previously described. Each of the flexible elements 68 has one end attached by a pin 45 to clip 43 and its other end attached to the curved surface 4| by a pin 46.

A similar flexible element t! has one end attached by a pin 58 to the opposite edge of the curved surface 4! and its other end engaged by a spring how 49 mounted in the clip 43 and serving to Y maintain the flexible elements 44, M and 4'! under tension.

Two sets'of fixedly supported flexible elements similar to the elements 44 and 41 may be provided to engage the curved surfaces 40, 4B of the spindle and to afford a support upon which the spindle may roll as in the form of construction 30 first described. These supportin'g flexible strips have been omitted from Figs. 13- and 14 to avoid confusion. It will readily be understood that with the spindle 38 supported in the manner indicated endwise movement of the driving pin 42 will cause a rolling movement of the spindle 39 Just as in the case of the spindle 20 in the first described construction. In; the present modified construction because of the larger radius of curvature of the. spindle the latter is made wider to provide for a requisite rolling or angular displace: ment.

' To the top end of the spindle is attached a pen arm having a tracing point 50a and the length of the pen arm to the trac ng point is made equal 45 to the radius of curvature of the surfaces 40, 4B

, as shown in Fig. 14. Thus when movement ofthe plane on which the spindle 39 may be considered to roll.

From a comparison of the construction shown in Figs. 13 and 14 with that shown in Figs. 1 to l2it will'be seen that the flexible elements ll, 44 and 4! correspond to and are equivalent to the end elements or portionsjlb, 29b and 29a of the flexible member 29 which extend over and in contact with a portion of the curved surface of the spindle to a longitudinal element of said surface and thence on straight lines tangent to the said surface. In the flrstdescribed construction the frictional engagement of the flexible members looped around the spindle '(supplement- (:5 ed if need be by the secm'ing pin 86) is relied upon to operativel'y connect the said end elements to the spindle,- whereas in the construction of Fig. 13 the pins 46 and ll perform that function.

-It will be obvious that the respective forms of the flexible members shown in Figs. 1-12 and Fig. 13,

as well as their methods of attachment to the spindle, can be used more or less interchangeably. My improved motion-converting and amplifying mechanism has various other applications than the oscillographs which have been described and as a further illustration of its possible application I have shown in Fig. 15 its application to an electric relay device. Here the apparatus comprises a casing and supporting frame construction 5| containing a piano-electric unit (not shown), a motion-converting and magnifying mechanism 52 driving a relay arm 53 which carries a contact 54 at its free end to cooperate with fixed contacts '5 and 56 adiustably mounted on a bracket S'Icarried by the casing structure 5|. The apparatus shown in Fig. 15 is throughout substantially similar to the corresponding parts illustrated in the other figures of the drawings, except that the contact devices are substituted for the pen point and the means for the feeding of ink are omitted.

It willbe apparent that my improved motion magnifying and converting mechanism is reversible so that driving forces applied to the angularly moving arm of the spindle will convert the angular motion of such arm to linear motion of the parts H or 42 of the above described mechanisms, the motion of the parts I! or 42 being in this case greatly reduced in comparison with the motion of the swinging arm. Furthermore,

it will be apparent that the specific forms of arrangement and construction of parts which characterize the mechanisms illustrated can be widely varied without departing from the invention as defined in the appended claims.

What I claim is:

1. In a motion-converting device, the combination of a spindle having a plurality of convexly curved lateral surfaces of two different radii and disposed on the same side-of the axis of rotation of the spindle; means for operatively supporting the spindle comprising two flexible tension elements each operatively connected at one of 40 its ends to the spindle and operatively engaging curved surface portions of the same radius and the two elements extending in opposite circumferential directions over said surface portions to a longitudinal line deflningelements of said surface portions and thence on straight lines tangent to the surface portions, and fixed supporting 5 means for the extended ends of the tension elements adapted to maintain tension therein; two other flexible tension elements similarly connected to the spindle in operative engagement with curved spindle surface portions of the other radius and similarly disposed in relation to the spindle; a tension means attached to the extended ends of the latter flexible elements and adapted to maintain tension therein; and means to longitudinally move one of the latter flexible elements toward and the other away from their respective points of tangency with the spindle and alternately similarly to move the one element away from and the other element toward their respective points of tangency with the spindle, thereby effecting angular movement of the spindle alternately in opposite directions.

2. A motion-converting device as set forth in claim 1 having at least two curved surfaces of one radius and a corresponding number of pairs of oppositely extending flexible elements cooperating with said surfaces to operatively support the spindle,

3. A motion-converting device as set forth in claim 1 having means operatively connected to the spindle adapted to trace the movement of a point on the axis of rotation of the spindle.

4. A motion-converting device as set forth in claim 1 having motion tracing means operatively connected to the spindle and extending laterally '5 to a distance from the line of tangency between the spindle and its flexible supporting elements which is greater than the difference between the two radii of the curved surfaces of the spindle.

CHARLES K. GRAVLEY. 

